Chapter 23-8: Pheochromocytoma

TEXTBOOK PRESENTATION

The classic presentation is a patient with attacks of paroxysmal hypertension, headache, palpitations, and sweating occurring several times daily, weekly, or every few months. Patients generally have orthostatic hypotension on physical exam.

DISEASES HIGHLIGHTS

1. 85–90% of patients have headache, sweating, or palpitations.

2. 10% of pheochromocytomas are malignant and tend to have a less typical presentation.

3. 10–15% are familial (multiple endocrine neoplasia type 2, von Hippel-Lindau disease, neurofibromatosis); these are more often asymptomatic (and normotensive) than sporadic cases.

4. Table 23-11 lists symptoms, taken from a series of patients with pheochromocytoma, about half of whom presented with paroxysmal hypertension and about half of whom had persistent hypertension.

EVIDENCE-BASED DIAGNOSIS

1. Pretest probability of 0.5% in hypertensive patients who have suggestive symptoms, and of 0.2% in unselected hypertensive patients

   Pheochromocytoma is rare even in patients with suggestive symptoms.

2. Pretest probability of 5% in patients with incidentally discovered adrenal masses

3. Plasma-free metanephrines is the single best test to rule out pheochromocytoma (Table 23-12).

   1. Patients should fast overnight and be supine for 30 minutes prior to the blood draw.

   2. Because caffeine and acetaminophen interfere with the assay, patients should avoid caffeine for 12 hours and acetaminophen for 5 days prior to testing.

   3. The standard upper limit of normal for plasma metanephrines is 61 ng/L.

      1. The overall (sporadic and hereditary cases) sensitivity at this cut off is 99% with a specificity of 89% (LR+ = 9; LR– = 0.01).

      2. A plasma metanephrine > 236 ng/L is 100% specific for the diagnosis of pheochromocytoma.

4. Patients with positive biochemical testing should undergo adrenal imaging.

   1. CT: sensitivity of 88–100% for detecting adrenal pheochromocytomas, 90% for extra-adrenal tumors; specificity 70–80% (LR+, 3.76; LR–, 0.08)

   2. MRI: sensitivity 90%; specificity also 70–80%; better than CT for identifying vascular invasion (LR+, 3.6; LR–, 0.13)

   3. ¹²³I-MIBG or positron emission tomography scanning is sometimes used when the biochemistry is positive and both CT and MRI are normal; sensitivity, 82–88%; specificity, 82–84% (LR+, 5; LR–, 0.18).